Fig. 6. Electron microscopic images of purified acetylcholine receptors from electric rays show them to be dimers. The affinity-purified acetylcholine receptor from H. monopterigium was viewed under the electron microscope in negative stain and is shown in A. Receptor dimers are evident in this (boxes in A) and all other acetylcholine receptor preparations isolated on the TDAC affinity column: (B) T. marmorata; (C) N. tasmaniensis.